Browsing by Author "Chabi, J."
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Item Education and Socio-economic status are key factors infuencing use of insecticides and malaria knowledge in rural farmers in Southern Côte d’Ivoire(BMC Public Health, 2022) Kouamé, R.M.A.; Ouattara, A.F.; Donnelly, M.J.; Guglielmo, F.; Abo, K.; Chabi, J.; Sedda, L.; Edi, C.; Sedda, L.Background: Insecticides play a key role in rural farming; however, their over- or misuse has been linked with a negative impact on malaria vector control policies. This study was conducted amongst agricultural communities in Southern Côte d’Ivoire to identify which insecticides are used by local farmers and how it relates to the perception of farmers on malaria. Understanding the use of insecticides may help in designing awareness programme on mosquito control and pesticides management. Methods: A questionnaire was administered to 1399 farming households across ten villages. Farmers were interviewed on their education, farming practices (e.g. crops cultivated, insecticides use), perception of malaria, and the diferent domestic strategies of mosquito control they use. Based on some pre-defned household assets, the socio economic status (SES) of each household was estimated. Statistical associations were calculated between different variables, showing significant risk factors. Results: The educational level of farmers was significantly associated with their SES (p<0.0001). Most of the householders (88.82%) identified mosquitoes as the principal cause of malaria, with good knowledge of malaria resulting as positively related to high educational level (OR=2.04; 95%CI: 1.35, 3.10). The use of indoor chemical compounds was strongly associated to the SES of the households, their education level, their use of ITNs and insecticide in agricultural (p<0.0001). Indoor application of pyrethroid insecticides was found to be widespread among farmers as well as the use of such insecticide for crops protection. Conclusion: Our study shows that the education level remains the key factor infuencing the use of insecticides by farmers and their awareness of malaria control. We suggest that better communication tailored to education level and including SES, controlled availability and access to chemical products, should be considered when designing campaigns on use of pesticides and vector borne disease control for local communityItem Efficacy of two PBO long lasting insecticidal nets against natural populations of Anopheles gambiae s.l. in experimental huts, Kolokopé, Togo(PLoS ONE, 2018-07) Ketoh, G.K.; Ahadji-Dabla, K.M.; Chabi, J.; Amoudji, A.D.; Apetogbo, G.Y.; Awokou, F.; Glitho, I.A.LLINs containing an insecticide plus the synergist, piperonyl butoxide (PBO) have been designed for increased efficacy against pyrethroid-resistant malaria vectors. In this study, two LLINs with PBO, PermaNet® 3.0 and Olyset® Plus, and a pyrethroid-only LLIN, Yorkool®, were evaluated in experimental huts against a free-flying, wild population of Anopheles gambiae s.l. in Kolokopé, a cotton cultivated area of Togo. WHO susceptibility tube tests and subsequent molecular assays determine the An. gambiae s.l. populations to be resistant to pyrethroids and DDT with both target site kdr and metabolic resistance mechanisms involved in the resistance observed. Anopheles gambiae s.s. and An. coluzzi were present in sympatry though the kdr (L1014F) mutation was observed at a higher frequency in An. gambiae s.s. The experimental hut results showed that both PermaNet® 3.0 and Olyset® Plus nets induced similar levels of deterrence, exophily, and reduced blood feeding rate against wild An. gambiae s.l. in contrast to the pyrethroid only LLIN, Yorkool®. The proportion of wild An. gambiae s.l. killed by unwashed PermaNet® 3.0 was significantly higher than unwashed Olyset® Plus (corrected mortality 80.5% compared to 66.6%). Similar blood feeding inhibition rates were observed for unwashed PermaNet® 3.0 and Olyset® Plus; however, PermaNet® 3.0 washed 20 times demonstrated significantly higher blood feeding inhibition rate than Olyset® Plus washed 20 times (91.1% compared with 85.6% respectively). Yorkool® performed the worst for all the parameters evaluated. In an area of pyrethroid resistance of An. gambiae s.l involving kdr target site and metabolic resistance mechanisms, LLINs with PBO can provide additional protection in terms of reduction in blood feeding and increase in mosquito mortality compared to a pyrethroid-only net, and should be considered in malaria vector control strategies.Item Evaluation of piperonyl butoxide in enhancing the efficacy of pyrethroid insecticides against resistant Anopheles gambiae s.l. in Ghana(Malaria Journal, 2017) Dadzie, S.K.; Chabi, J.; Asafu-Adjaye, A.; Owusu-Akrofi, O.; Baffoe-Wilmot, A.; Malm, K.; Bart-Plange, C.; Coleman, S.; Appawu, M.A.; Boakye, D.A.Background: Malaria vector control methods involving the use of pyrethroids remain the strategies being used against malaria vectors in Ghana. These methods include the use of long-lasting insecticidal nets and indoor residual spraying in many areas in Ghana. However, there is evidence that pyrethroid resistance is widespread in many areas in Ghana. Synergists have been shown to be useful in inhibiting the enzymes that are responsible for the development of resistance and hence enhance the insecticide susceptibility of Anopheles gambiae sensu lato (s.l.) in many areas. The present study investigated the effect of piperonyl butoxide (PBO) on the susceptibility status of An. gambiae s.l. across some sentinel sites in Ghana. Methods: Three to five day old An. gambiae s.l. reared from larvae were used in WHO susceptibility tube assays. Batches of 20-25 female adult An. gambiae s.l. were exposed simultaneously to the insecticide alone and to the PBO + insecticide. The knock down rate after 60 min and mortality at 24 h were recorded. Results: Deltamethrin and permethrin resistance of An. gambiae s.l. was observed in all the sites in 2015 and 2016. The mortality after 24 h post exposure for deltamethrin ranged from 16.3% in Weija to 82.3% in Kade, whereas that for permethrin ranged from 3.8% in Gomoa Obuasi to 91.3% in Prestea. A significant increase in susceptibility to deltamethrin and less to permethrin was observed during both 2015 and 2016 years in most of the sites when An. gambiae s.l. mosquitoes were pre-exposed to PBO. Conclusion: Findings from this study showed that the use of PBO significantly enhanced the susceptibility of An. gambiae s.l. mosquitoes in most of the sentinel sites. It is recommended that vector control strategies incorporating PBO as a synergist can be effective in killing mosquitoes in the presence of deltamethrin and permethrin resistance. © 2017 The Author(s).Item High insecticide resistance intensity of Anopheles gambiae (s.l.) and low efficacy of pyrethroid LLINs in Accra, Ghana(Parasites & Vectors, 2019-06-05) Dadzie, S.K.; Pwalia, R.; Joannides, J.; Iddrisu, A.; Addae, C.; Acquah‑Baidoo, D.; Obuobi, D.; Amlalo, G.; Akporh, S.; Gbagba, S.; Athinya, D.K.; Hadi, M.P.; Jamet, H.P.; Chabi, J.Background: Insecticide resistance of Anopheles gambiae (s.l.) against public health insecticides is increasingly reported in Ghana and need to be closely monitored. This study investigated the intensity of insecticide resistance of An. gambiae (s.l.) found in a vegetable growing area in Accra, Ghana, where insecticides, herbicides and fertilizers are massively used for plant protection. The bioefficacy of long-lasting insecticidal nets (LLINs) currently distributed in the country was also assessed to delimitate the impact of the insecticide resistance intensity on the effectiveness of those nets. Methods: Three- to five-day-old adult mosquitoes that emerged from collected larvae from Opeibea, Accra (Ghana), were assayed using CDC bottle and WHO tube intensity assays against different insecticides. The Vgsc-L1014F and ace- 1 mutations within the population were also characterized using PCR methods. Furthermore, cone bioassays against different types of LLINs were conducted to evaluate the extent and impact of the resistance of An. gambiae (s.l.) from Opeibea. Results: Anopheles gambiae (s.l.) from Opeibea were resistant to all the insecticides tested with very low mortality observed against organochlorine, carbamates and pyrethroid insecticides using WHO susceptibility tests at diagnostic doses during three consecutive years of monitoring. The average frequencies of Vgsc-1014F and ace-1 in the An. gambiae (s.l.) population tested were 0.99 and 0.76, respectively. The intensity assays using both CDC bottle and WHO tubes showed high resistance intensity to pyrethroids and carbamates with survivals at 10× the diagnostic doses of the insecticides tested. Only pirimiphos methyl recorded a low resistance intensity with 100% mortality at 5× the diagnostic dose. The bioefficacy of pyrethroid LLINs ranged from 2.2 to 16.2% mortality while the PBO LLIN, PermaNet ® 3.0, was 73%. Conclusions: WHO susceptibility tests using the diagnostic doses described the susceptibility status of the mosquito colony while CDC bottle and WHO tube intensity assays showed varying degrees of resistance intensity. Although both methods are not directly comparable, the indication of the resistance intensity showed the alarming insecticide resistance intensity in Opeibea and its surroundings, which could have an operational impact on the efficacy of vector control tools and particularly on pyrethroid LLINs. Keywords: Anopheles gambiae (s.l.), WHO susceptibilityItem High Levels of Knockdown Resistance in Anopheles coluzzii and Anopheles gambiae (Diptera: Culicidae), Major Malaria Vectors in Togo, West Africa: A 2011 Monitoring Report(Journal of Medical Entomology, 2013-03-29) Chabi, J.; Ahadji-Dabla, K.M.; Amoudji, A.D.; Nyamador, S.W.; Apétogbo, G.W.; Glitho, I.A.; Ketoh, G.K.A survey of susceptibility to DDT, deltamethrin, bendiocarb, and chlorpyrifos-methyl was conducted in five localities in 2011 in Togo, West Africa, to assess the insecticide resistance status of Anopheles gambiae s.l. (Diptera: Culicidae). Female populations of An. gambaie s.l. emerged from collected larvae (F0) were exposed to insecticide-impregnated papers using World Health Organization test kits for adult mosquitoes; the susceptible reference strain Kisumu was used as a control. Resistance to DDT and deltamethrin was observed within the mosquito populations tested. Anopheles gambiae s.s. and Anopheles coluzzii represented the only species recorded in the study sites. The frequency of knockdown resistance (kdr L1014F) mutation determined using polymerase chain reaction diagnostic tests was lower in An. gambiae than in An. coluzzii in all of the localities except Kolokopé. Further investigations of An. gambiae s.l. resistance are needed in Togo to help the National Malaria Control Programme in vector control decision making and implementation of resistance management strategy.Item Microsporidia MB is found predominantly associated with Anopheles gambiae s.s and Anopheles coluzzii in Ghana(Springer Nature, 2021) Akorli, J.; Akorli, E.A.; Tetteh, S.N.A.; Amlalo, G.K.; Opoku, M.; Pwalia, R.; Adimazoya, M.; Atibilla, D.; Pi‑Bansa, S.; Chabi, J.; Dadzie, S.K.A vertically transmitted microsporidian, Microsporidia MB, with the ability to disrupt Plasmodium development was reported in Anopheles arabiensis from Kenya, East Africa. To demonstrate its range of incidence, archived DNA samples from 7575 Anopheles mosquitoes collected from Ghana were screened. MB prevalence was observed at 1.8%. An. gambiae s.s constituted 87% of positive mosquitoes while the remaining were from An. coluzzii. Both sibling species had similar positivity rates (24% and 19%; p = 0.42) despite the significantly higher number of An. gambiae s.s analysed (An. gambiae s.s = 487; An. coluzzii = 94; p = 0.0005). The microsporidian was also more prevalent in emerged adults from field-collected larvae than field-caught adults (p < 0.0001) suggestive of an efficient vertical transmission and/or horizontal transfer among larvae. This is the first report of Microsporidia MB in Anopheles mosquitoes in West Africa. It indicates possible widespread among malaria vector species and warrants investigations into the symbiont’s diversity across sub-Saharan Africa.Item Rapid high throughput SYBR green assay for identifying the malaria vectors Anopheles arabiensis, Anopheles coluzzii and Anopheles gambiae s.s. Giles(PLoS ONE, 2019-04) Chabi, J.; Van’t Hof, A.; N’dri, L.K.; Datsomor, A.; Okyere, D.; Njoroge, H.; Pipini, D.; Hadi, M.P.; De Souza, D.K.; Suzuki, T.; Dadzie, S.K.; Jamet, H.P.The Anopheles gambiae sensu lato species complex consists of a number of cryptic species with different habitats and behaviours. These morphologically indistinct species are identified by chromosome banding. Several molecular diagnostic techniques for distinguishing between An. coluzzii and An. gambiae are still under improvement. Although, the current SINE method for identification between An. coluzzii and An. gambiae works reliably, this study describes a refinement of the SINE method to increase sensitivity for identification of An. coluzzii, An. gambiae and An. arabiensis based on amplicon dissociation curve characteristics. Field-collected samples, laboratory-reared colonies and crossed specimens of the two species were used for the design of the protocol. An. gambiae, An. coluzzii, and hybrids of the two species were sampled from Ghana and An. arabiensis from Kenya. Samples were first characterised using conventional SINE PCR method, and further assayed using SYBR green, an intercalating fluorescent dye. The three species and hybrids were clearly differentiated using the melting temperature of the dissociation curves, with derivative peaks at 72˚C for An. arabiensis, 75˚C for An. gambiae and 86˚C for An. coluzzii. The hybrids (An. gambiae / An. coluzzii) showed both peaks. This work is the first to describe a SYBR green real time PCR method for the characterization of An. arabiensis, An. gambiae and An. coluz-zii and was purposely designed for basic melt-curve analysis (rather than high-resolution melt-curve) to allow it to be used on a wide range of real-time PCR machines.Item Resistance to pirimiphos-methyl in West African Anopheles is spreading via duplication and introgression of the Ace1 locus(PLOS, 2021) Grau-Bove, X.; Lucas, E.; Pipini, D.; Rippon, E.; van ‘t Hof, A.E.; Constant, E.; Dadzie, S.; Egyir-Yawson, A.; Essandoh, J.; Chabi, J.; Djogbe´nou, L.; Harding, N.J.; Miles, A.; Kwiatkowski, D.; Donnelly, M.J.; Weetman, D.Vector population control using insecticides is a key element of current strategies to prevent malaria transmission in Africa. The introduction of effective insecticides, such as the organo phosphate pirimiphos-methyl, is essential to overcome the recurrent emergence of resis tance driven by the highly diverse Anopheles genomes. Here, we use a population genomic approach to investigate the basis of pirimiphos-methyl resistance in the major malaria vec tors Anopheles gambiae and A. coluzzii. A combination of copy number variation and a sin gle non-synonymous substitution in the acetylcholinesterase gene, Ace1, provides the key resistance diagnostic in an A. coluzzii population from Coˆte d’Ivoire that we used for sequence-based association mapping, with replication in other West African populations. The Ace1 substitution and duplications occur on a unique resistance haplotype that evolved in A. gambiae and introgressed into A. coluzzii, and is now common in West Africa primarily due to selection imposed by other organophosphate or carbamate insecticides. Our findings highlight the predictive value of this complex resistance haplotype for phenotypic resistance and clarify its evolutionary history, providing tools to for molecular surveillance of the current and future effectiveness of pirimiphos-methyl based interventions.